How much does DA affect Horsepower?
Race Director
Joined: Jan 2003
Posts: 15,176
Likes: 87
From: State of Confusion
On Memorial Day Monday of 1992, friends (who'd didn't know how to find the track ) convinced me to go racing (i.e. : LEAD-them ) at Quaker City Dragway, competing in their 'Memorial Day Classic':
I had attended a few mid-week test-n-tune sessions @ QCD, and my Z28 had always run between 13.34 & 13.28.
In 2 pre-race time-runs, it went 13.31 and 13.30, and with a storm due to blow-in, the Track Officials tried to hurry the program along, where I was lucky-enough to win the 1st Round with a 13.29:
after a short-but-hectic storm, track-drying began, and as evening approached, the air cooled-off, but there was very little humidity in the air, with swirling winds.
When racing resumed, I ran a 13.21 on a 13.26 dial-in, yet won when my opponent ran .12 under:
all my incrementals 'jived', so as the air got even-better, I dialed 13.18 for round #3, where my opponent fouled, and I progressed, running a 13.16!
Totally in the dark, I dialed 13.11 for round #4, as the incrementals made-sense, and my weather-station recorded better-yet atmospheric conditions, and I won with a 13.10x, although I burped the throttle, having a slightly-better RT than my opponent:
my incrementals said it'd have run an .09, so I dialed 13.07 for the Quarter-Final Round, and ran dead-on with change (13.074 ), advancing to the Semi-Finals, and an odd-lot/bye-run into the Final round.
Already running 2-tenths quicker than I ever had at that track, I simply 'read' what the incrementals and weather-data said, and dialed 13.06 for my competition single, and ran 13.06x:
in the Final Round, I dialed 13.05, and ran a 13.071, winning when my opponent, who'd been lifting on every run he'd made all-day and 'guessing' what to dial, ran .1-under, ON THE BRAKES, trying to come-around me at the stripe.
I pocketed $750 CA$H, left the track, and never won another Round of eliminations at that track (VERY tough competition there ), and never ran any quicker than 13.26 there, either:
my ET on that day alone varied .25x-seconds.....
I had attended a few mid-week test-n-tune sessions @ QCD, and my Z28 had always run between 13.34 & 13.28.
In 2 pre-race time-runs, it went 13.31 and 13.30, and with a storm due to blow-in, the Track Officials tried to hurry the program along, where I was lucky-enough to win the 1st Round with a 13.29:
after a short-but-hectic storm, track-drying began, and as evening approached, the air cooled-off, but there was very little humidity in the air, with swirling winds.
When racing resumed, I ran a 13.21 on a 13.26 dial-in, yet won when my opponent ran .12 under:
all my incrementals 'jived', so as the air got even-better, I dialed 13.18 for round #3, where my opponent fouled, and I progressed, running a 13.16!
Totally in the dark, I dialed 13.11 for round #4, as the incrementals made-sense, and my weather-station recorded better-yet atmospheric conditions, and I won with a 13.10x, although I burped the throttle, having a slightly-better RT than my opponent:
my incrementals said it'd have run an .09, so I dialed 13.07 for the Quarter-Final Round, and ran dead-on with change (13.074 ), advancing to the Semi-Finals, and an odd-lot/bye-run into the Final round.
Already running 2-tenths quicker than I ever had at that track, I simply 'read' what the incrementals and weather-data said, and dialed 13.06 for my competition single, and ran 13.06x:
in the Final Round, I dialed 13.05, and ran a 13.071, winning when my opponent, who'd been lifting on every run he'd made all-day and 'guessing' what to dial, ran .1-under, ON THE BRAKES, trying to come-around me at the stripe.
I pocketed $750 CA$H, left the track, and never won another Round of eliminations at that track (VERY tough competition there ), and never ran any quicker than 13.26 there, either:
my ET on that day alone varied .25x-seconds.....
Le Mans Master
Joined: Nov 2003
Posts: 8,308
Likes: 157
From: NJ
The one other thing I will add is that although better da will yield more hp it doesn't mean you'll go faster. More hp may= more spinning. Your ability to put that hp to the ground will determine how much you can decrease your et.
I've run in some killer da's only to go .2 slower because the track was too cold to obtain ample traction. It's not only on the launch where you spin, the tires will spin on the shifts especially in a manual.
I've run in some killer da's only to go .2 slower because the track was too cold to obtain ample traction. It's not only on the launch where you spin, the tires will spin on the shifts especially in a manual.
Race Director
Joined: Jan 2003
Posts: 15,176
Likes: 87
From: State of Confusion
Crisp air and a cold surface translates to more-HP and less-grip, resulting in Goodyear Tire & Rubber Company working extra shifts to replace inventory of slicks.
Race Director
Joined: Oct 2001
Posts: 19,653
Likes: 428
From: Melbourne Florida
Cruise-In IV Veteran
DA was the cause of my stupidity last Saturday...getting only one time shot in 80* temps, I knew when we were called for the first round at 6:30PM I was in trouble...at this time of year the temps drop like a rock after 5 PM or so...makes it murder to dial my car without a TAG (I don't have one)....I am sure I would have been in the 13.50's after running 13.75 in the time shot...btw, both runs were dead hooks so I went .2 faster 2 1/2 hours later purely due to lower DA...
Thread Starter
Race Director
Joined: Mar 2000
Posts: 17,602
Likes: 20
From: Palm City Florida
DA was the cause of my stupidity last Saturday...getting only one time shot in 80* temps, I knew when we were called for the first round at 6:30PM I was in trouble...at this time of year the temps drop like a rock after 5 PM or so...makes it murder to dial my car without a TAG (I don't have one)....I am sure I would have been in the 13.50's after running 13.75 in the time shot...btw, both runs were dead hooks so I went .2 faster 2 1/2 hours later purely due to lower DA...
Between 2 to 3 tenths swing between good and bad DA....
minus another 3 to tenths for using drag radials...
On a good night I might see the 11's....
Melting Slicks
Joined: Nov 2004
Posts: 2,799
Likes: 2
From: Cape Coral FL
On Memorial Day Monday of 1992, friends (who'd didn't know how to find the track ) convinced me to go racing (i.e. : LEAD-them ) at Quaker City Dragway, competing in their 'Memorial Day Classic':
I had attended a few mid-week test-n-tune sessions @ QCD, and my Z28 had always run between 13.34 & 13.28.
In 2 pre-race time-runs, it went 13.31 and 13.30, and with a storm due to blow-in, the Track Officials tried to hurry the program along, where I was lucky-enough to win the 1st Round with a 13.29:
after a short-but-hectic storm, track-drying began, and as evening approached, the air cooled-off, but there was very little humidity in the air, with swirling winds.
When racing resumed, I ran a 13.21 on a 13.26 dial-in, yet won when my opponent ran .12 under:
all my incrementals 'jived', so as the air got even-better, I dialed 13.18 for round #3, where my opponent fouled, and I progressed, running a 13.16!
Totally in the dark, I dialed 13.11 for round #4, as the incrementals made-sense, and my weather-station recorded better-yet atmospheric conditions, and I won with a 13.10x, although I burped the throttle, having a slightly-better RT than my opponent:
my incrementals said it'd have run an .09, so I dialed 13.07 for the Quarter-Final Round, and ran dead-on with change (13.074 ), advancing to the Semi-Finals, and an odd-lot/bye-run into the Final round.
Already running 2-tenths quicker than I ever had at that track, I simply 'read' what the incrementals and weather-data said, and dialed 13.06 for my competition single, and ran 13.06x:
in the Final Round, I dialed 13.05, and ran a 13.071, winning when my opponent, who'd been lifting on every run he'd made all-day and 'guessing' what to dial, ran .1-under, ON THE BRAKES, trying to come-around me at the stripe.
I pocketed $750 CA$H, left the track, and never won another Round of eliminations at that track (VERY tough competition there ), and never ran any quicker than 13.26 there, either:
my ET on that day alone varied .25x-seconds.....
I had attended a few mid-week test-n-tune sessions @ QCD, and my Z28 had always run between 13.34 & 13.28.
In 2 pre-race time-runs, it went 13.31 and 13.30, and with a storm due to blow-in, the Track Officials tried to hurry the program along, where I was lucky-enough to win the 1st Round with a 13.29:
after a short-but-hectic storm, track-drying began, and as evening approached, the air cooled-off, but there was very little humidity in the air, with swirling winds.
When racing resumed, I ran a 13.21 on a 13.26 dial-in, yet won when my opponent ran .12 under:
all my incrementals 'jived', so as the air got even-better, I dialed 13.18 for round #3, where my opponent fouled, and I progressed, running a 13.16!
Totally in the dark, I dialed 13.11 for round #4, as the incrementals made-sense, and my weather-station recorded better-yet atmospheric conditions, and I won with a 13.10x, although I burped the throttle, having a slightly-better RT than my opponent:
my incrementals said it'd have run an .09, so I dialed 13.07 for the Quarter-Final Round, and ran dead-on with change (13.074 ), advancing to the Semi-Finals, and an odd-lot/bye-run into the Final round.
Already running 2-tenths quicker than I ever had at that track, I simply 'read' what the incrementals and weather-data said, and dialed 13.06 for my competition single, and ran 13.06x:
in the Final Round, I dialed 13.05, and ran a 13.071, winning when my opponent, who'd been lifting on every run he'd made all-day and 'guessing' what to dial, ran .1-under, ON THE BRAKES, trying to come-around me at the stripe.
I pocketed $750 CA$H, left the track, and never won another Round of eliminations at that track (VERY tough competition there ), and never ran any quicker than 13.26 there, either:
my ET on that day alone varied .25x-seconds.....
Excellent job of judging conditions.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
100' is roughly .01
The deal is each 1,000' is worth about 3% in HP at the crank; on a 300chp SBC that amouns to 10Hp or 1mph = .1sec (if you can hook it up).
A 30deg F change in temp will have a similar effect, assuming RH & baro stay constant.
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Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 264
From: St. Louis, MO
St. Jude Donor '08
And you better get comfortable with the idea of some pretty high rpm launches....
Which actually feel MUCH less violent to me than a bog, by the way.
Watch the videos in this thread:
http://forums.corvetteforum.com/show....php?t=1605999
Watching this in person taught me how to launch. Along with Ranger's posts. I do it by sound now.
Last edited by Joe_G; Feb 5, 2007 at 02:07 AM.
Thread Starter
Race Director
Joined: Mar 2000
Posts: 17,602
Likes: 20
From: Palm City Florida
Chuck, I had to learn a few tricks to get my car there. I suggest you come to our next Private Test day. That is when you will learn to launch your car - that's where it matters.
And you better get comfortable with the idea of some pretty high rpm launches....
Which actually feel MUCH less violent to me than a bog, by the way.
Watch the videos in this thread:
http://forums.corvetteforum.com/show....php?t=1605999
Watching this in person taught me how to launch. Along with Ranger's posts. I do it by sound now.
And you better get comfortable with the idea of some pretty high rpm launches....
Which actually feel MUCH less violent to me than a bog, by the way.
Watch the videos in this thread:
http://forums.corvetteforum.com/show....php?t=1605999
Watching this in person taught me how to launch. Along with Ranger's posts. I do it by sound now.
Thanks Joe!!! Sick video!..
My rims arrive this Thursday and I expect to go to Roger shortly after to have the Drag Radials mounted..
I want to attend a private track day so bad.. I have the hardened output shaft upgrade and the Cartek Clutch.. I should be ok for some pretty high rpm launches assuming the DR's hold...
The Cartek clutch is pretty tolerant to intentional slippage at high rpms without glazing over..
I fricken love that thing..
Race Director
Joined: Aug 2000
Posts: 10,649
Likes: 31
From: Central Florida
Ranger
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 264
From: St. Louis, MO
St. Jude Donor '08
Thanks Joe!!! Sick video!..
My rims arrive this Thursday and I expect to go to Roger shortly after to have the Drag Radials mounted..
I want to attend a private track day so bad.. I have the hardened output shaft upgrade and the Cartek Clutch.. I should be ok for some pretty high rpm launches assuming the DR's hold...
The Cartek clutch is pretty tolerant to intentional slippage at high rpms without glazing over.. I fricken love that thing..
My rims arrive this Thursday and I expect to go to Roger shortly after to have the Drag Radials mounted..
I want to attend a private track day so bad.. I have the hardened output shaft upgrade and the Cartek Clutch.. I should be ok for some pretty high rpm launches assuming the DR's hold...
The Cartek clutch is pretty tolerant to intentional slippage at high rpms without glazing over..
I fricken love that thing..Based on my 5 years of lurking here and 3 years of steadily drag racing a vette, I believe that most problems with rears and clutches are caused by dumping the clutch or wheel hopping on street tires. There is a fine line between smoking the clutch and having a great launch, but if you listen to Robert's launches a few times that's how to do it. Not too long of a slip, and certainly not too short.
Talking to a new Z06 owner last week who's learning his car, he put it well. It's like learning to drive a stick again! You have to balance the clutch out with pressing the gas pedal...... to maintain traction, minimize burn of the clutch, yet keep the engine in the powerband to prevent bog. It's actually easier than it sounds I think.
I have excellent HP tuners log graphs of me doing it which sheds some good light on how to do it, you can see the revs vs. the mph vs the throttle position all in a graph segregated by time. I have found studying them very helpful, I will show them to you next time we're at the track.
I think Ranger has HP Tuners logs too... I wish he'd share his!
Race Director
Joined: Aug 2000
Posts: 10,649
Likes: 31
From: Central Florida
I've instrumented my car with various audio, video and data logging devices to better understand the effects of driver-variables and then explain best practices in my DVD on max acceleration.
The mix of sensor inputs is very helpful.
Ranger
The mix of sensor inputs is very helpful.
Ranger
Thread Starter
Race Director
Joined: Mar 2000
Posts: 17,602
Likes: 20
From: Palm City Florida
Thread Starter
Race Director
Joined: Mar 2000
Posts: 17,602
Likes: 20
From: Palm City Florida
Where can I get a copy?
Thread Starter
Race Director
Joined: Mar 2000
Posts: 17,602
Likes: 20
From: Palm City Florida
Imagine pulling a weight across a table top with a rubber band. The object is to pull the weight across the table as fast as possible without reaching the limits of the rubber band and snapping it.. (break traction)
You must keep the rubber band at max stretch point BUT just below the point of breakage. (i.e. Throttle position). I know.. I am nuts..
Race Director
Joined: Aug 2000
Posts: 10,649
Likes: 31
From: Central Florida
It's in the works, and when available, word will spread pretty fast. 
On the MT Street Radials, you'll need to remember the burnout proceedure differences.
(1) first pass of the day, full smokey burnout
(2) all other passes that day, spin the tires to first smoke. MT calls that "hazing" the tires.
If, instead, you do the full burnout on the 2d-thru-N pass, the tread gets greasy, and you'll produce 1-2 tenths worse 60'.
That difference in burnout procedures confounds many drivers until remedied.
Ranger
On the MT Street Radials, you'll need to remember the burnout proceedure differences.
(1) first pass of the day, full smokey burnout
(2) all other passes that day, spin the tires to first smoke. MT calls that "hazing" the tires.
If, instead, you do the full burnout on the 2d-thru-N pass, the tread gets greasy, and you'll produce 1-2 tenths worse 60'.
That difference in burnout procedures confounds many drivers until remedied.
Ranger
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 264
From: St. Louis, MO
St. Jude Donor '08
MT drag radials in the rain
I'll mention one other thing regarding these MT drag radials - I just got a new set and have about 200 miles on them and maybe 12 passes.
Yesterday I had a family emergency and had to go to the hospital in the pouring superbowl weather with my DR's on. Odd, 2nd Superbowl in a row I spent at the ER and no, I don't beat my kids or wife, just coincidence.
I decided on the way home to test out their wet weather traction, and frankly I was very surprised - when new, these things grip LIKE CRAZY in the rain. I actually had a hard time turning them over with traction control off. When I got home I felt the tread and it was very sticky like after a burnout.
I did not hit deep standing water and would not suggest doing so - I'm sure they hydroplane badly at high speed. But with full tread and with fresh rubber, they have real grip even in the rain so long as you don't have standing water.
Yesterday I had a family emergency and had to go to the hospital in the pouring superbowl weather with my DR's on. Odd, 2nd Superbowl in a row I spent at the ER and no, I don't beat my kids or wife, just coincidence.
I decided on the way home to test out their wet weather traction, and frankly I was very surprised - when new, these things grip LIKE CRAZY in the rain. I actually had a hard time turning them over with traction control off. When I got home I felt the tread and it was very sticky like after a burnout.
I did not hit deep standing water and would not suggest doing so - I'm sure they hydroplane badly at high speed. But with full tread and with fresh rubber, they have real grip even in the rain so long as you don't have standing water.
